Abstract
The stability of the subthreshold swing (SS) is quite important for switch and memory applications in logic circuits. The SS in our MoS2 field effect transistor (FET) is enlarged when the gate voltage sweep range expands towards the negative direction. This is quite different from other reported MoS2 FETs whose SS is almost constant while varying gate voltage sweep range. This anomalous SS enlargement can be attributed to interface states at the MoS2–SiO2 interface. Moreover, a deviation of SS from its linear relationship with temperature is found. We relate this deviation to two main reasons, the energetic distribution of interface states and Fermi level shift originated from the thermal activation. Our study may be helpful for the future modification of the MoS2 FET that is applied in the low power consumption devices and circuits.
Highlights
Transition metal dichalcogenides (TMDCs) are leading the trend of studying various two-dimensional (2D) materials
Among the device performance stability issues caused by the interface states, the enlargement of subthreshold swing (SS) will slow down the switch speed and hugely increase the static power consumption of field effect transistor (FET), which will hinder the use of MoS2 FETs in low-power applications [9,10]
For MoS2 FETs, threshold voltage shift and hysteresis are mainly caused by the interface states acting as charge traps at the
Summary
Transition metal dichalcogenides (TMDCs) are leading the trend of studying various two-dimensional (2D) materials. As a 2D material, because of the extremely high surface-to-volume ratio, the properties of MoS2 FETs, such as threshold voltage, hysteresis, on/off ratio, and SS, can be affected by interface states at the interface between the MoS2 channel and the gate dielectric [5,8]. During the sweep of gate voltage, the interface states are electrically equivalent to an additional capacitance which is first in parallel to the semiconductor capacitance, and their result is series to the oxide capacitance by exchanging electrons with the MoS2 channel, sabotaging the stability of MoS2. Note that the SScan canbe properties of MoS2 FETs whose SS is typically more than 1000 mV/dec [11]. For the first time, an obvious deviation of SS from its with linearity with temperature forobserved the backgated nm SiO
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